Hi Peter,
I'm not sure if I understand your question. By the way, most private is unlikely to be the least costly; serious encryption on large WAN provider networks is a serious dollar question. The biggest and most expensive ISP's have the best security, the medium and smaller ones don't. Cox is pretty much universally reqarded as the most secure ISP service in the U.S., but it may not be available in your locale.
Depending on where you live, you may not have easesment for a 2nd landline phone company, as this usually isn't available in private residences, only in commercial properties such as businesses. I know because last large company I worked for we had to have a 2nd phone company landline into our building, because of power and phone service outtages, we had to have 24x7 dialback capabillity on our products (SAN storage boxes), so our Customers could dial back into our Customer service servers night or day, so we couldn't rely on just 1 phone company. There are many requirements to get this service, and you'll have to contact BOTH phone companies to see what the easement issues are in your physical location to do so. If you live in an unrestricted area, this may be possible with existing telephone wiring, but you can expect it be very, VERY expensive. This costs us thousands of dollars a month back in 1999 when we implemented, so I don't expect that solution has come down very much in cost.
You might be better served by using a reliable Satellite ISP provider such as Dish Network or AT&T Direct TV. They can hook up a dish to your home or apartment and their decoder box can bring off a digital telephone line that connects to the closest CO of a different phone Company than you are aready using; this might be many miles away even if you live in an urban area. This home phone line would give you landline & Fax capabilities just like your existing Comcast service does (do you know who your home phone landline company is, as Comcast is NOT a Phone Company. It would be someone like Verizon, GTE, or AT&T). This could also be confusing for you, as many folks thing that Comcast, Time-Warner, and other large ISPs are phone company and landline providers which they are not. The restriction here is that if you are doing Fax communication via Sat. dish phone lines, you probably won't be able to communicate with older Fax machines on analog lines. Digital Cordless Phone and Fax technology you and your sender/receiver are using must be restricted to Digital communication only--analog won't work without physical landline connection to your local CO (which you are no doubt using now).
In the answer to your other question about the least cost of a Gateway versus a Modem (ie: Cable Modem, not a DSL Modem); generally Gateways are more complex devices; 1 of the main ISPs in my area uses those (Charter), and they cost about 3 times to lease over the cost of a Cable Modem. The last few years, Charter here would install a Cable Modem, then a Gateway, and a customer-provided router or wifi router which would cost around $350-$400 US to lease, plus $100 for the router if you leased that as well, so somewhere around $500 total cost 18-36 mos. on most service contracts, and this is the case with several of my business customers. As technology is changing, Charter here is replacing their devices with a single device to perform Cable Modem/Gateway/Router functionality along with built-in wifi for some Customers, at about a third of the lease cost. (maybe $175 lease cost over 2 yrs.) I've seen a few of these, where the ISP (Charter) came out and serviced the customer's connection and replaced all 3 of their boxes with one of these new jobs, at a fraction of the cost. They are very secure, and have resisted all my attempts at cracking into them to view/adjust their internal configurations. Charter here maintains that box a non-CPE or not Customer Premises equipment, which means that a Customer has to call a Charter Tech to get into their box, they won't let a Customer or even a Computer Guy like me get into their box. They troubleshoot it all behind the scenes, and either fix it or replace it--so it you wanted security settings downgraded or upgraded for example, the Customer or the Tech (me) is not allowed in to make that change; it takes a phone call to Charter Tech Support to do so. This is a royal pain with the new ones, since you can't easily troubleshoot someones home wifi network if you can't access the router config part of the device (used to be a separate box like you have now).
Anyway, having worked for multiple phone companies, I do have a little insider knowledge. Hopefully, this helped you a bit.
You asked for alternate suggestions, which I gave you, and the Sat. dish solution may be your cheapest. Also, they are very secure. I have had no problems with security with either of them.
Post back if you have more questions.
Best of luck,
<<<BIGBEARJEDI>>>
